Common Defects in Welding Area of ​​Spiral Welded Steel Pipe

Submerged arc welding area prone to defects such as stomata, hot cracks, and undercut.

1, bubble. Bubble occurred in the middle of the bead, the main reason is that hydrogen is still in the form of bubbles hidden in the weld metal inside, so the elimination of this defect is the first measure must be removed welding wire and weld rust, oil, moisture and moisture And other substances, followed by the need to dry the flux to remove moisture. In addition, to increase the current, reduce the welding speed, slow down the melting rate of molten metal is also very effective.

2, sulfur crack (sulfur caused by the crack). Cracks in the segregation of sulfur in the segregated zone of the plate (especially soft boiled steel). The reason for this is that there is hydrogen present in the sulfur segregation zone containing low melting point iron sulfide and steel. Therefore, in order to prevent this situation, the use of sulfur segregation with less semi-killed steel or sedative steel is also effective. Second, the weld surface and flux cleaning and drying is also very necessary.

3, hot crack. In submerged arc welding, hot cracks can be generated in the weld bead, especially in arcs and arcs. In order to eliminate such cracks, usually in the arc and arc at the installation of the plate, and the end of the coil at the end of welding, the spiral welded pipe can be reversed welding welding. Hot cracking is most likely to occur when the weld stress is large, or when the weld metal is very high.

4, the accumulation of slag. Involved in the welding residue is in the weld metal remnants of a part of the slag.

5, poor penetration penetration. Inside and outside the weld metal overlap is not enough, sometimes not penetrated. This situation is called insufficient penetration.

6, undercut The undercut is a V-shaped groove along the weld centerline at the edge of the weld. The undercut is generated when the welding speed, current, voltage and other conditions are not appropriate. Where the welding speed is too high than the current is not suitable for more likely to cause undercut defects.